Many areas (e.g. the Sea of Okhotsk) in the world have seasonal sea ice zones. The extent of the seasonal sea ice zone and the sea ice volume greatly affect the energy exchange between the atmosphere and the ocean. For this reason, it is an important factor for meteorological observation to detect a seasonal sea ice zone.
In particular, thin ice having a thickness of not more than 30 cm is of critical significance in controlling the heat, salt, and vapor fluxes at the ocean surface. Thus, detecting and classifying the thin ice using remote sensing technology is of particular importance.
Up to now, many researches for a distribution of sea ice thicknesses or classification of ice types are performed by using a microwave radiometer or a synthetic aperture radar.
However, data obtained from these researches are rarely discussed in relation to actually observed values of ice thicknesses except for comparison with observed values of ice thickness obtained by a submarine-borne sonar in the polar zones.
Especially, the Sea of Okhotsk has few actual measurements of ice thicknesses. The actual measurements have been rarely compared with values obtained by a microwave sensor/radar.
Therefore, the present invention has as object to provide a method of observing sea ice for calculating an ice draft of desired sea ice from data obtained by a synthetic aperture radar.